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https://issues.apache.org/jira/browse/FLINK-6888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16046319#comment-16046319
]
ASF GitHub Bot commented on FLINK-6888:
---------------------------------------
Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4105#discussion_r121321436
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/utils/UserDefinedFunctionUtils.scala
---
@@ -329,6 +337,41 @@ object UserDefinedFunctionUtils {
}
}
+
+ /**
+ * Internal method of AggregateFunction#getAccumulatorType() that does
some pre-checking
+ * and uses [[TypeExtractor]] as default return type inference.
+ */
+ def getAccumulatorTypeOfAggregateFunction(
+ aggregateFunction: AggregateFunction[_, _],
--- End diff --
Can we abstract a method according ` getAccumulatorTypeOfAggregateFunction`
and `getResultTypeOfAggregateFunction`. just like follows:
```
def getTypeByMethodOrTypeExtractor(
aggregateFunction: AggregateFunction[_, _],
clazz: Class[_],
methodName: String,
candidateType: TypeInformation[_] = null): TypeInformation[_] = {
val resultType = try {
val method: Method = aggregateFunction.getClass.getMethod(methodName)
method.invoke(aggregateFunction).asInstanceOf[TypeInformation[_]]
} catch {
case _: NoSuchMethodException => null
case ite: Throwable => throw new TableException("Unexpected
exception:", ite)
}
if (resultType != null) {
resultType
} else if(candidateType != null) {
candidateType
} else {
try {
TypeExtractor.createTypeInfo(clazz).asInstanceOf[TypeInformation[_]]
} catch {
case ite: InvalidTypesException =>
throw new TableException(
s"Cannot infer type of $clazz" +
s"You can override AggregateFunction.$methodName to specify the
type.", ite)
}
}
}
```
I'm not sure whether it is the best way, Please let me know what you think?
> Can not determine TypeInformation of ACC type of AggregateFunction when ACC
> is a Scala case/tuple class
> -------------------------------------------------------------------------------------------------------
>
> Key: FLINK-6888
> URL: https://issues.apache.org/jira/browse/FLINK-6888
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Jark Wu
> Assignee: Jark Wu
> Fix For: 1.4.0
>
>
> Currently the {{ACC}} TypeInformation of
> {{org.apache.flink.table.functions.AggregateFunction[T, ACC]}} is extracted
> using {{TypeInformation.of(Class)}}. When {{ACC}} is a Scala case class or
> tuple class, the TypeInformation will fall back to {{GenericType}} which
> result in bad performance when state de/serialization.
> I suggest to extract the ACC TypeInformation when called
> {{TableEnvironment.registerFunction()}}.
> Here is an example:
> {code}
> case class Accumulator(sum: Long, count: Long)
> class MyAgg extends AggregateFunction[Long, Accumulator] {
> //Overloaded accumulate method
> def accumulate(acc: Accumulator, value: Long): Unit = {
> }
> override def createAccumulator(): Accumulator = Accumulator(0, 0)
> override def getValue(accumulator: Accumulator): Long = 1
> }
> {code}
> The {{Accumulator}} will be recognized as {{GenericType<Accumulator>}}.
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